Inductance



June 30, 1942- N. E. DAVIS Erm. 2,288,516

INDUCTANCE Filed June 22, 1959 2 Sheets-Sheet l 42/ 4 4Z] BY ATTORNEY.

yJune 30, 1942. N. E. DAvls ET AL.

INDUCTANGE Filed June 22, 1939 2 Sheets-Sheet 2 m u L M m M N ATTORNEY.

Patented June 30, 1942 INDUCTAN CE Norman Eustace Davis, Frederick Gawn Robb,

and Henry James Craymer, Chelmsford, England, assignors to Radio Corporation ofAmer ica, a corporation of Delaware Application June 22, 1939, Serial No. 280,468 In Great Britain July 29, 1938 6 Claims. (Cl. 178-44) This invention relates to inductances and more particularly to adjustable inductances suitable for use in high power short wave radio transmitters and for similar purposes.

The invention seeks to provide improved inductances of such construction as to be easily and quickly variable, and easily and quickly connectable in a variety of different Ways (series, parallel or series-parallel) without requiring the use of special tools such as spanners or indeed of tools of any kind; in which the contact surfaces through which connection is made are smooth, capable of carrying large currents, and rmly held together under high pressure without the use of ordinary clamping bolts and nuts and without requiring the use of spanners; and in which sharp edges, ,such as are provided by ordinary nuts and bolts, are avoided so that the ilash-over voltages between different members follow a substantially true law of radius and spacing.

According to this invention, an adjustable inductance element comprises a plurality of metallic tubes adapted to telescope into one another, an expansible member inside the innermost tube, and means, manually operable externally of the telescoping tubes, for expanding said expansible member to abut against the inside of said innermost tube thereby to cause the tubes to bind against one another and prevent telescoping action.

The invention is illustrated in the accompanying drawings which show one embodiment of the invention. 'I'his embodiment was designed for use as the adjustable anode inductance of the nal power amplifier of a 100 kw. short wave transmitter. The gures are to different scales but all are drawn in true proportion.

In the drawings:

Fig. 1 is a'front view `of the general arrangement;

Fig. 2 is a side view of the general arrangement;

Fig. 3 is a sectional elevation of one of the telescopic tube inductances A or Figs. 1 and 2;

Fig. 4 is an elevation of the inner cylinder of one of the inductances A.

Figs. 5 and 6 are respectively face and side elevations of the expansion ring of Fig, 3;

Figs. 7 and 8 are respectively a sectional elevation and an end view of the cylinder head of Figa:

Fig. 9 is an end view of one o1' the ttings B of Figs. 1 and 2 Fig. 10 is a sectional elevation on the line XY of Fig. 9;

Fig. 11 is a. section on the line PQ of Fig. 10; and

Fig. 12 is a developed view of the clasp of Fig. 9.

Referring now to the drawings, the construction therein shown is for a short wave transmitter in which the high frequency circuits are mounted on trucks which can be run into the set after adjustment for wave length. In Figs. 1 and 2, the broken lines indicated by TR represents a truck having pedestals PD (which in the example in question correspond electrically to the anodes of the valves in a push-pull circuit) on which the inductance members are mounted either directly or through insulators as may be desired. The inductance assembly consists of a plurality of telescopic tube inductances A, each of which is individually adjusted, connected in series, parallel, or series-parallel by tubular fittings B of adjustable position. The number and positions of the ttings B are chosen to suit the connections required and may be changed quickly and easily 'to give different connections for different inductance values.

Each telescopic tube inductance A comprises a brass base Al in which is soldered a brass connection stud A|2 and on which is fixed an inner cylinder A2 of copper having a longitudinal saw cut.A2 with chamfered edges. Fitted over the cylinder A2 is an outer cylinder A3 also o1' copper, with a brass disc A4 tted into it near one end. The disc A4 is xed by locating pegs A4 and is also soldered to the tube A3. Fixed, as by soldering, in a central aperture in the disc AI is a copper tubular support A5 to the other end of which is ilxed, as by soldering, a brass expansion disc A8 formed with a bevelled edge A6' as shown, and with a central aperture and an oiset aperture A6". The letter aperture A6 is for receiving a brass dowel pin All which is carried by a brass expansion head A8 which is bevelled at A8' to correspond with the bevelling at A6'. The head A8 is ilxed on the end of an expansion rod AIS which is screw threaded at the other end AIS to t into the internally screw threaded central boss Alll of a brass hollow cylinder head AHI. The head AIB is formed with a. peripheral step AIU" as best shown in Fig. '7 adapted rotatably to t into the outer end of the cylinder A3. Fitted into the V-like space between the beveled edges A8', A6 is an expansion ring A1 consisting of a helically wound phosphor bronze Wire of 18- S. W. G. The member A1 is thus a spring ring capable of being increased in diameter against its springiness.

To adjust the length of and therefore the 1nductance of a member A the head AIU is rotated in' a direction to separate the parts A6, A8 thus allowing the ring A1 to contract and is then pushed or pulled longitudinally until the overall length of the whole telescopic member A is that required. The head Alll is then rotated in the opposite direction to force the parts A6, A8 towards each other, thus expanding the ring A1 and locking the telescoping parts A2, A3 firmly in the adjusted position, the ring A1 pressing against the part A2 and forcing it to expand inside of and grip the part A3.

Adjustable connections between the parts A are made by tubular fittings B, as shown in Figs.

9 to l2. Each of these ttings comprises a rotatable copper tube Bl centrally of which is fixed a brass turning plate B2 with a central square aperture B2 adapted to t fairly freely over a square sectioned brass turnbuckle B4. In each end of the tube BI is rotatably fitted a brass clamp B8, the outer end of which is formed to act as a seat for a member AA. On each of the threaded vends of the turnbuckle is a brass nut member B5 of cylindrical shape with the threaded orifice at right angles to the axis of the cylinder. On eachnut member B5 is tted one end of a phosphor bronze clasp B1, the other end of which is xed to the seating face of the appropriate clamp B8. As' will be obvious from Figs. 9 to l2, by rotating the tube BI in the appropriate direction relative to the clamps B8, the clasps B1 may be drawn in tight so as to firmly grip members A between them and the clamps B8. Thus, the members B can be quickly and easily released from the members A, moved to any required positions along them, and then equally quickly firmly clamped in the new positions.

As will be obvious, all the members B, in any one inductance assembly, need not be of the same length, nor, for the matter of that, need be all the members A. The drawings, therefore, although drawn in diierent scales for different gures, are intended to show the manner of construction rather than the actual sizes.

What is claimed is:

l. An adjustable inductance element comprising a plurality of metallic tubes adapted to telescope into one another, an expansible member located inside the innermost tube, and means manually operable externally of the telescoping tubes for expanding said expansible/ member to abut against the inside of said innermost tube thereby to cause the tubes to bind against one another and prevent telescoping action.

2. Ari inductance element comprising two tubes adapted to telescope into one another, the inner tube having a longitudinal cut therein, an expansble spring ring inside said inner tube and carried by a structure supported from the outer tube, said. structure comprising an expander for side of the inner tube and expand it to grip the outer tube.

3. An element as claimed in claim 2 wherein,

the expander comprises two disc-like members with bevelled edges together defining a V-line space in which the ring is seated, so that when said members are drawn towards one another the ring is expanded, means including a longitudinally movable rod being provided for drawing the said members towards one another.

4. An inductance element comprising a pair of metallic tubes adapted to telescope into one another, a base member and a rounded over head, said base member. secured to the innermost tube and the rounded head rotatably mounted in the outermost tube, an expandable ring member located within the innermost tube which includes two disc-like members having beveled edges facing each other to denne a V line space for seating said expandable ring, said ring arranged within the innermost tube so that when said disc-like members are drawn toward each other the ring expands, means for drawing said disc-like members together including a longitudinal rod threaded at one end thereof to engage threads in said rounded-over head member, the other end of said rod secured to one of said discs and arranged to slide through the other disc.

5. In combination in an adjustable inductance assembly a plurality of inductance elements as claimed in claim 1 with a plurality of connectors between said elements and adjustable with respect thereto, each connector comprising ay tubular member with clasp and clamp members at the ends, each clamp in co-operation with its clasp, being adapted to embrace an inductance element, said clasp and clamp members being arranged to be simultaneously tightened upon the elements embraced thereby by rotating said tubular member relative to the clasp and clamp members.

6. In combination in an adjustable inductance assembly a plurality of inductance elements as claimed in claim l with a plurality of connectors between said elements and adjustable with respect thereto, each connector comprising a tubular member having a turnbuckle with nut members at the threaded ends thereof, each nut member being nxed to one end, with clasp and metal strap clamp members at the ends, each clamp in co-operation with its clasp, being adapted to embrace an inductance element, said clasp and clamp members being arranged to be simultaneously tightened upon the elements embraced thereby by rotating said tubular member relative to the clasp and clamp members.

NORMAN EUSTACE DAVIS. FREDERICK GAWN ROBB. HENRY JAMES CRAYMER. 

